CVE-2026-63362 in open62541
Summary
by MITRE • 07/31/2026
An unsigned integer underflow in the PubSub signature verification path in open62541 may allow a remote attacker to cause a denial of service via a crafted UDP packet.
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Analysis
by VulDB Data Team • 07/31/2026
The vulnerability described represents a critical integer underflow condition within the PubSub signature verification mechanism of the open62541 OPC UA stack implementation. This flaw exists specifically within the unsigned integer arithmetic operations that handle signature validation processes, creating a potential vector for remote attackers to disrupt system availability. The issue manifests when processing crafted UDP packets through the PubSub communication pathway, which is commonly used in industrial automation and IoT environments where real-time data exchange is critical.
The technical root cause stems from improper bounds checking during unsigned integer calculations within the signature verification logic. When an attacker crafts malicious UDP packets with carefully manipulated parameters, the system's unsigned integer variables can underflow to extremely large values, causing unexpected behavior in the verification algorithms. This underflow condition typically occurs when subtracting a larger value from a smaller unsigned integer, resulting in wraparound behavior that can bypass security checks or cause memory corruption patterns. The vulnerability is particularly dangerous because it operates at the protocol level where signature verification should ensure data integrity and authenticity.
Operational impact of this vulnerability extends beyond simple denial of service to potentially compromise the entire communication infrastructure within OPC UA-based systems. Remote attackers can exploit this condition to repeatedly trigger the underflow scenario, causing continuous service disruption that may affect industrial control systems, smart grid implementations, or manufacturing automation networks where open62541 is deployed. The nature of the vulnerability means that legitimate traffic could be disrupted while the system attempts to process malformed packets, leading to cascading failures in real-time data transmission. This represents a significant concern for operational technology environments where continuous availability is paramount.
Mitigation strategies should focus on immediate code-level patches that implement proper bounds checking and input validation before unsigned integer operations occur. Organizations should deploy firmware updates from open62541 maintainers as soon as patches become available, while also implementing network segmentation and packet filtering rules to limit exposure to potentially malicious traffic. Network monitoring solutions should be configured to detect unusual patterns in PubSub traffic that might indicate exploitation attempts. Additionally, security teams should consider implementing intrusion detection systems specifically tuned to identify the signature patterns associated with this vulnerability class. This issue aligns with CWE-191 (Integer Underflow) and represents a potential ATT&CK technique for denial of service operations within industrial control environments.